Tuesday, 6 October 2009

Using a cost model for digital curation, based on the functional breakdown from OAIS. Multiply break down activities until get to costable components; loos rather frightening. Have use case for digital migration. Cost factors include format interpretation, software provision (development of reader, writer & translator). Interesting data in person weeks for development of migration, eg TIFF to PDF/A as 34.7 person weeks (!!)

Reporting results of some earlier stuff; A-archives dating 1968-1998; very heterogeneous; B & C archives more recentand more homogeneous. Shows results from model predictions and actual costs, differences mostly because the A archives were so hard. Also, for the better archives, the mode did well overall but under-estimated some parts and over-estimated other parts.

Second test case was migration of 6 TB of data in 2000 files (very big ones: 300 MByte each). They bought software; the model over-estimated the “development” time on this basis, but under-estimated the processing, perhaps because of the very big files; throughput was very low.

Overall, they found that detailed cost factors make the model not an accurate predictor (but still useful). Precision an issue; models are inaccurate per se, but sometimes give impression of accuracy.

Searching for studies on format life expectancy and migration frequency [longer and less in my view].

Question: how about software re-use? They cost on a first mover basis. Also migration tools do also become obsolete.

Question: why did you think migrating from PDF was necessary? Hardly a format at risk. Turns out to be a move from proprietary to non-proprietary.

Question on scaling: thousands to hundreds of millions of objects; will these apply. Answer was that they will. [CR: doubt this; biggest flaw in LIFE so far has been devastating scaling problems.]

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